1. Field of the Invention
The present invention relates to the field of telescoping tubular members, such as extension poles and the like, and more particularly to an interior sleeve which locks in place and provides wear resistance between outer and inner tubular members.
2. Background of the Invention
Telescoping tubular members are in use in a number of applications; for example, in cleaning windows, extension poles are used to extend the reach of a squeegee or other tool by the window washer. Extension poles are a series of concentric tubes of increasing diameter stored within each other so that as additional length is needed, a tube with a smaller diameter is pulled out, extended to the desired length, and locked in place. The tool is attached to the end of the unit with the smallest diameter.
There are various means for locking extension poles together when in use, some of them are exterior locking devices and others have interior locking mechanisms, such as that shown in U.S. Pat. Nos. 4,856,929 or 4,238,164, for example. Extension poles with an interior clamping device can provide a smooth unobstructed exterior surface which is preferred by many window washers as the poles are pulled through the user's hands.
Although the adjacent poles of the extension poles are very close in diameter, some spacing is necessary between the inner wall of an outer tube and the outer wall of the next smaller inner tube, to allow for assembly and for ease in sliding the poles during use. Because of this spacing the tubes will bang against each other when subjected to vigorous use, eventually causing wear on the individual extension units and on the rest of the pole, including the locking mechanism. Accordingly, a sleeve such as that shown in FIG. 2 was developed to fit between two telescoping poles and operate as a bushing to facilitate their slidability relative to each other and to provide wear resistance. This prior art sleeve is made of an Acetal plastic, such as Delrin.RTM. plastic from DuPont, for a smooth sliding surface. It has a narrow longitudinal slot to accommodate an internal ridge in the tubular member. It is inserted into the larger of two tubular members and secured by adhesive to the inner surface of that pole. This assembly procedure is very inefficient and frustrating since the slippery surface is required for ease in slidability of the poles, but such a surface is unreceptive for most adhesives. With this prior art sleeve, adhesive is applied to the sleeve before it is inserted in the pole and the pole must then be left undisturbed for some time to dry. After extensive use by window washers under conditions where the pole is exposed to water and cleaning solutions, the adhesion would frequently fail and the sleeve would slip out. Without the sleeve to act as a stop at one end of the pole, the inner pole could be over-extended and pulled out entirely from the outer pole.
Thus, there has been a need, particularly for extension poles for window washers, for a bushing or sleeve to reduce the wear of the telescoping poles on each other and to increase the fit of different-sized poles. This sleeve must be smooth for easy slidability of the poles, yet securely attached to the poles. The present invention provides such a sleeve. It can be made out of any smooth plastic or slippery material desired, since it is secured to the poles by a snap-in action and requires no adhesive. It provides for a better fit of the poles with each other, which reduces the friction and wear on the poles and also increases the precision of the tool mounted on the extension pole. In a typical extension pole, it also provides a permanent stop for the locking mechanism and prevents the inner pole from being entirely removed from the outer pole. Thus, the invention provides a unique solution to the problems of the prior art.